Airbrake

ABSTRACT

A device is disclosed for controlling the duration of an administration of a prescribed dose of dry powder to a user&#39;s lung when inhaling the powder by use of a dry powder inhaler (DPI). The present device controls the speed of a moving cassette ( 4 ) carrying medical powder doses to one by one be administered by the DPI to a user. Generally the dose is pre-metered and applied to the cassette in the form of a strip ( 31 ) or a series of spots of ready-prepared powder. The present device using the airbrake arrangement ( 22 ) prolongs the time during which the pre-metered powder dose is released to the inhalation air. Adjustment means of the airbrake arrangement ( 22 ) define leakage of air ( 36 ) and thereby motion speed of a spring-loaded cassette ( 4 ). During the motion of the cassette the powder dose is sucked from the prepared dose powder strip onto the cassette ( 4 ) by a nozzle ( 1 ) connected to a mouthpiece used for inhaling medical powder from the dry powder inhaler.

TECHNICAL FIELD

The present invention relates to a dry powder inhaler for administrationof a medical dry powder to the lungs of a user, and more exactly to anairbrake device for prolonging the time for dose delivery uponinhalation.

BACKGROUND

Today supply and distribution of medical powders take place in manydifferent ways. Within health care more and more is focussed on thepossibility to dose and distribute powder directly to the lungs of auser by means of an inhaler to obtain an efficient, fast, and userfriendly administration of the specific medical substance.

Inhalers have been developed from being very simple to the up-to-daterelatively complicated devices. For the up-to-date inhalers some form ofdosing process is almost entirely used for preparing the dose to beinhaled. Most often the dosing of the amount to be inhaled takes placeindustrially in advance in a dose package containing of the order 5-50doses. The inhaler then is loaded with this dose package as the sourceof each dose. Other inhalers have a magazine from which the powder isdosed by some device for distribution to the inspiration air. In bothcases the powder will generally be strongly agglomerated and thereforemust be dispersed.

This dispersion of the agglomerates today mainly takes place by means oftechniques in which the energy of the inspiration air is utilized. Anormal inhalation takes place during about two seconds and a peacefulinspiration takes 3-4 seconds. In such designs, in which only theinhalation air is utilized for the de-agglomeration, only a fraction ofthe energy of the inhalation air will be utilized, as the dose of powderis given normally during only 0.1 to 0.4 s. Consequently this results ina low exploitation of the available energy which, as a matter of fact,will be present in the inhalation air. As only a small portion of theamount of energy is used it will be too low for a sufficientde-agglomeration to take place. The total respirable dose thereforebecomes very dependent on the occasion and the individual user andthereby very varying from time to time. To improve this condition anumber of inhalers include some kind of device against which the powdershould collide and thereby transfer energy for de-agglomerating thepowder. However, such a collision with a fixed or mechanically movingobject involves that a relatively large amount of powder sticks eitherpermanently or is transported further together with the next dose. Inboth cases this constitutes a negative factor for the goal of obtaininga high accuracy and quality of the inhaled dose, e.g. an accurate amountof powder having a high portion of very small particles.

In a document WO97/00704 is described an inhaler device in which thesubstance to be administered is charged electrostatically and the dosingis performed by means of the assistance of a rotating dosing drumattracting the charged particles of the substance. The substance is thenemitted from the dosing drum by means of a combination of an additionalelectric field and the air stream resulting from an inspiration. Inadvance of a desired dosing step the substance to be administered iskept in a reservoir, loaded for instance by means of receiving acartridge containing the substance intended for many operations of thedevice.

However here is still a demand for simple means for prolonging a dosedelivery during an inhalation to obtain a full effectiveness of apre-metered medical powder dose administered to a user's lung.

SUMMARY

The present invention discloses a device for controlling the duration ofan administration of a prescribed dose of dry powder to a user's lungwhen inhaling the powder by means of a dry powder inhaler (DPI). Thepresent device controls the speed and time characteristics of a movingcassette carrying medical powder doses to one by one be administered bythe DPI to a user. Generally the dose is pre-metered and applied to thecassette in the form of a strip or a series of spots of ready-preparedpowder. An airbrake device prolongs the time during which thepre-metered powder dose is released to the inhalation air. Adjustmentmeans of the airbrake device define the motion speed of a motion ofspring-loaded cassette during which the powder dose is sucked from theprepared dose powder strip onto the cassette by a nozzle connected to amouthpiece.

A device for controlling dosing speed and timing of an inhaler device isset forth by the independent claim 1, and further embodiments are setforth by the dependent claims 2 to 7.

DESCRIPTION OF THE DRAWINGS

The invention will be described in the form of a preferred andilluminating embodiment and by means of the attached drawings whereinlike reference numbers indicate like or corresponding elements andwherein:

FIG. 1 illustrates a principal sketch of an airbrake in the form of acylinder;

FIG. 2 illustrates another principal sketch of the airbrake in the formof bellows;

FIG. 3 illustrates a principal sketch of the internals of the inhalerwith the airbrake illustrated in the form of a bellows and with therelevant parts in their respective positions prior to an inhalation bythe user;

FIG. 4 illustrates a principal sketch of the internals of the inhalerwith the airbrake illustrated in the form of a bellows and with therelevant parts in their respective positions shortly after theinhalation by the user has begun; and

FIG. 5 illustrates a principal sketch of the internals of the inhalerwith the airbrake illustrated in the form of a bellows and with therelevant parts in their respective positions when the inhalation by theuser has ended.

DESCRIPTION OF THE INVENTION

When a user starts to inhale through the mouthpiece of the DPI, thecassette is released from its start position and begins to movepropelled by a drive spring. In the preferred embodiment a compressionspring is used, but it is equally possible to use a spring working inthe expansion mode, indeed the force may come from other sources e.g.hydraulic or pneumatic. The cassette is carrying pre-metered dosespreferably in the form of strips of powder. The powder preferablyconstitutes an electro-powder having well defined electrostaticproperties as well as forming a major fine particle fraction withparticles of a size preferably between 0.5 and 5 μm.

The device according to the present invention is coupled to the cassettecarrying the prepared doses and acts as an airbrake, which controls inan administering process the speed and the timing of the movingcassette. The selected dose to be administered from the cassette istransported from the moving cassette via air sucked by means of a nozzle1 of the suction tube 33, comprising besides the nozzle 1 a diffuser 2and a porous tube 3, all of which fitted to the mouthpiece (FIG. 3). Asthe flow of inhaled air flows past the dose before going into thenozzle, the powder of the dose is sucked up and dispersed into this airfor the length of time it will take for the dose onto the movingcassette to pass by the nozzle 1. Thus the airbrake controls thedelivery of the dose. The delivery can be set from a high concentrationin a short time to a low concentration in a long time and anything inbetween. A continuous administration of the dose is made possibleTypically this time span is of the order of 0.2-4 seconds.

The object of designing and including an airbrake as an important partof a dry powder inhaler is to control the time during which the dose isdelivered to the user. This is an important factor in achieving theoverall goal of a continuous dose delivery to the user and in making alocal or system delivery possible or a combination thereof. It is easyto adjust the speed and timing of the cassette and thereby the time ittakes to administer the dose by increasing or decreasing the brakingaction of the airbrake device by changing one or more of itscharacteristics.

The airbrake device is preferably in the form of a variable volume ofconfined air, which is coupled to the DPI body 8 and the moving cassette4. Preferably the airbrake is arranged such, that it is forced to expandor contract when the cassette 4 moves in relation to the body. In thepreferred embodiment the confinement can be in the form of a bellows ora cylinder with a piston, but also other embodiments are possible. Thecontinuous braking action, which controls the speed of the cassette 4 isachieved by letting air into or out of the airbrake device through acontrolled leakage, e.g. through one or more holes connecting thevariable volume with the surrounding atmosphere. In the case of cylinderwith piston a small gap between the piston and the cylinder will beanother possibility.

In FIGS. 1 and 2 are presented two illustrative embodiments of anairbrake device 22 enclosing a regulated volume of air 36 in accordancewith the present invention.

For a better understanding of the mode of operation of the airbrakedevice only the vital internal parts of an inhaler are illustrated in anillustrative embodiment according to FIGS. 3, 4 and 5. The airbrake isillustrated as a bellows 22, but other embodiments of the airbrake areequally possible, e.g. a piston 21 and cylinder 20 arrangement asillustrated in FIG. 1, and this and all other alternative embodimentsare included as accepted variations of the present invention. Thoseskilled in the art can no doubt see several possible ways of applyingthe airbrake in a DPI, but common to all cases is that one end of theairbrake is fixed directly or indirectly to the body 8 of the DPI andthe other end is fixed directly or indirectly to a moving dose carrier,also referred to as the cassette 4. In FIG. 3 are shown the relativepositions of the vital internal parts of the DPI in the loaded stateprior to an inhalation by the user. For the sake of simplicity, theillustrations of FIGS. 3, 4 and 5 show the cassette member in the formof a cylinder carrying doses 31 arranged on the cylindrical surface inrectangular beds with the long axis parallel to the axis of thecassette. The motion of the cassette while delivering the dose isnormally in a straight line along the longitudinal axis, butalternatively a rotation around the axis or a combination of rotationand linear motion will be possible, depending on the geometry of thedose distribution on the cassette member.

FIG. 4 shows the cassette shortly after beginning to inhale, theinhalation releasing the cassette from its loaded ready-to-go state bymeans of a release mechanism that is not part of the present inventionand not illustrated in the figures. The cassette 4 is propelled forwardby the drive spring 9 with a speed determined by the force of the spring9 and the braking action of the air brake 22. The airbrake 22 then isforced to expand as the cassette moves forward.

Assuming a zero pressure difference between the surrounding atmosphereand the internal volume of the air brake device and provided there is noleakage of air between the surrounding atmosphere and the internalvolume of the air brake device, the braking power increases with thedistance of travel for the cassette. The reason being that the internalvolume of the airbrake is forced to increase as the cassette movesforward, which increases the induced vacuum in the then enlarged butenclosed volume of the airbrake device. This increasing difference inpressure between the internal vacuum and the external atmosphericpressure results in an increasing force, the braking force, which triesto push the airbrake back to its original size. At a certain distance oftravel the counteracting forces of the drive spring 9 and the air brake22 balance each other exactly and the cassette cannot move further.

By introducing a small controlled amount of leakage from the surroundingair to the internal air 36 volume of the airbrake the vacuum andconsequently the braking force will be reduced with time and allowingthe cassette to move forward along its path of motion with a controlledspeed.

Further the effects of a disturbance of the cassette movement arisingfor example by some mechanical imperfection or wear have to be accountedfor. In these cases the airbrake will automatically help to keep thespeed constant, because as the disturbance tries to slow down the movingcassette the braking action by the airbrake is simultaneously reduced,which increases the drive force of the spring that tries to overcome thedisturbance.

The air thus leaking into the airbrake arrangement is taken fromfiltered air inside the DPI body, eliminating the risk of dirty airclogging the aperture or apertures leaking air into the airbrakearrangement. Since the speed of the cassette is controlled such that itis repeatable from one dose to the next and if the geometry of thepre-metered dose strip is the same for all doses, the time to deliver adose will be constant.

In another embodiment of the invention it is possible to arrange the airbrake device such that the internal volume is forced to contract ratherthan expand by the moving cassette, creating an over pressure instead ofvacuum, but otherwise completely analogue to the principle of operationdescribed in the foregoing.

To minimize the power needed from the user to close the inhaler whenpushing the cover to the closed position, which tightens the drivespring and forces the airbrake back to its original size, the airbrakehas an additional air inlet with a check valve or similar arrangement,which lets air into or out of the variable volume, whichever the casemay be, so that the loading operation by the user is made as easy aspossible.

Also illustrated in FIG. 4 is a foil cutter 11 cutting open an aluminumfoil (not shown) that seals the recess 7 of the cassette surface forprotecting the underlying dose 31 on the dose bed in order to make aselected dose accessible to the air stream upon an inhalation. Thecutter is in a fixed position such that when the cassette is pushed pastthe cutter it cuts through the foil and opens it up just before thenozzle 1, which is part of the suction tube consisting of a nozzle 1, adiffuser 2 and a porous tube 3. Next the dose on the dose bed reachesthe point where the nozzle is positioned and as the cassette is pushedpast the nozzle, the inhaled air sucks up and disperses the powder ofthe dose in the stream of air and delivers the dose to the user for thepre-set amount of time.

In FIG. 5 the cassette has reached the end of its travel, the dosing iscompleted and the full dose has been delivered to the user.

Particularly the present invention will be of great interest in thedesign of a new continuous inhaler, which thereby will present a numberof advantages in comparison to prior art inhalers found on the markettoday and which commonly deliver a dose during a very short period oftime, often of the order 0.2 to 0.3 seconds.

The present invention has been described by means of an illustrativeembodiment for disclosing its operation, but it will be apparent to aperson skilled in the art, that there may be performed numerousmodification and changes to the present invention without departure fromthe object and scope thereof, which are defined by the appended claims

What is claimed is:
 1. A braking device controlling a time of release ofpowder from a dry powder inhaler comprising: a dose carrier to be put inmotion during an inhalation; a first force element; and a device memberenclosing a volume of air comprising an arrangement for letting out orletting in air into said device member at a selected rate; wherein thefirst force element and the device member are arranged so that, a firstforce exerted by this first force element causes a motion of the dosecarrier and a change in the enclosed volume of air in the device member,causing a change of pressure inside the device member, thereby forming asecond force counteracting the first force.
 2. The device according toclaim 1, wherein said device member comprises a cylinder with a pistonprovided with the arrangement for controlling leakage of air into or outof the enclosed volume.
 3. The device according to claim 2, wherein thefirst force element comprises a spring, the spring providing the exertedfirst force that is applied to an end surface of said dose carrier. 4.The device according to claim 3, wherein said spring is a compressionspring.
 5. The device according to claim 3, wherein said device memberand the spring are arranged so that each comes into close proximity of asame end surface of said dose carrier.
 6. The device according to claim3, wherein adjustment of said arrangement for controlling a leakage ofair changes a rate of the change in the enclosed volume of air in thedevice member.
 7. The device according to claim 3, wherein said devicemember and the spring are arranged so that each comes into contact witha same end surface of said dose carrier.
 8. The device according toclaim 2, wherein said arrangement for letting in or letting out air ofsaid device member comprises a check valve.
 9. The device according toclaim 1, wherein said device member comprises a bellows provided withthe arrangement for controlling a leakage of air into or out of theenclosed volume.
 10. The device according to claim 9, wherein the firstforce element comprises a spring, the spring providing the exerted firstforce for application to an end surface of said dose carrier.
 11. Thedevice according to claim 10, wherein said spring is a compressionspring.
 12. The device according to claim 10, wherein said device memberand the spring are arranged so that each comes into close proximity of asame end surface of said dose carrier.
 13. The device according to claim10, wherein adjustment of said arrangement for controlling a leakage ofair changes a rate of the change in the enclosed volume of air in thedevice member.
 14. The device according to claim 10, wherein said devicemember and the spring are arranged so that each comes into contact witha same end surface of said dose carrier.
 15. The device according toclaim 9, wherein said arrangement for letting in or letting out air ofsaid device member comprises a check valve.
 16. An inhaler devicecontaining a braking device, comprising: a body; a movable dose carrierinstalled in the device; an adjustable volume chamber attached to thebody, the adjustable volume chamber comprising a passage connecting aninterior and an exterior of the chamber; and a source of a first forceconnected between the body and the adjustable volume chamber; whereinthe first force bears on the moving dose carrier, and wherein when themoving dose carrier is moved with respect to the body by the firstforce, the volume of the adjustable volume chamber is changed.
 17. Theinhaler device of claim 16, wherein the change of the volume of theadjustable volume chamber causes a resistance to the first force as airis moved between the interior and the exterior of the adjustable volumechamber through the passage.
 18. The inhaler device of claim 17, whereinthe source of the first force comprises a spring.
 19. The inhaler deviceof claim 17, wherein the adjustable volume chamber comprises a cylinderand a piston arranged within the cylinder.
 20. The inhaler device ofclaim 17, wherein the adjustable volume chamber comprises a bellows. 21.The inhaler device of claim 17, wherein the adjustable volume chambercomprises a check valve, so that passage of the air in a first directionbetween the interior and the exterior of the chamber is resisted lessthan passage of the air in a second direction opposite the firstdirection.
 22. An inhaler with an installed dose carrier, comprising: abody; a dose carrier installed inside the body; a means for providing afirst force between the dose carrier and the body; an adjustable volumechamber connected to the body and the dose carrier, so that when thedose carrier is released from an initial position, the dose carriermoves with respect to the body and a volume of the adjustable volumechamber is changed, causing resistance to the movement of the dosecarrier.